(a) Field of the Invention
The present invention relates to a liquid crystal display, and in particular, to an RGB interface type liquid crystal display.
(b) Description of the Related Art
A typical liquid crystal display (LCD) includes an upper panel provided with a common electrode and a plurality of color filters and a lower panel provided with a plurality of thin film transistors (TFTs) and a plurality of pixel electrodes. Alignment layers are coated on inner surfaces of the upper and the lower panels, and a liquid crystal layer is filled in a gap between the alignment layers. The pixel electrodes and the common electrode are supplied with voltages, and the voltage difference between the two electrodes generates an electric field. When the strength and/or the direction of the electric field is changed, orientations of liquid crystal molecules in the liquid crystal layer is changed according thereto and the transmittance of light passing through the liquid crystal layer. Accordingly, desired images are obtained by controlling the voltage difference between the pixel electrodes and the common electrode.
In the meantime, small and medium LCDs are driven in two types, roughly. One is an RGB interface type and the other is a CPU interface type. The former separately inputs image data and control signals for chip driving, while the latter sequentially inputs the image data and the chip driving control signals.
A small LCD used for a mobile phone, etc., roughly includes a phone and a panel assembly.
The panel assembly corresponds to a display unit like a typical LCD, and the phone supplies various control signals for controlling the panel assembly.
An LCD employing RGB interface such as a mobile phone requires extremely low power consumption. Most of the power consumption depends on the speed or the frequency of a data enable signal.
The data enable signal indicates the existence of data by using its signal levels. For example, a high section of the data enable signal indicates the existence of data and a low section indicates the absence of data.
Generally, a small device such as a mobile phone transmits image data with a frequency of about 60 Hz. In the meantime, a data driver operates in synchronization with the frequency of the data enable signal. In detail, a memory incorporated in the data driver determines the writing of the data based on the levels of the data enable signal, and, for example, the data are written into the memory during the high section of the data enable signal. After the data are written in the memory, they are transmitted to the panel assembly to form images.
Meanwhile, since most of the image data for the mobile phone, etc., represent still images, the data stored in the memory can be repeatedly used. Accordingly, repeated writing of the same data is meaningless and causes the continuous operation of the data driver, thereby causing power consumption.